Automatic detector device for a tyre assembling-disasssembling machine

An automatic detector device for tyre assembling-disassembling machine having a wheel support (G) mounted for rotation about an axis of rotation of a tyred wheel (9) the bead of which is to be released, a pair bead-releasing roll-carrying extending-retracting arm (T 1 , T 2 ) supporting each a respective bead-releasing roll (R 1 , R 2 ) and located, in use, on opposite sides with respect to the tyred wheel (9). The detector device comprises at least one sensor member (3) movably supported at a respective bead-releasing roll (R 1 , R 2 ), driving means (5) for each sensor member (3), so that it can be moved between a retrieved rest position and an extended working position, and control means (34) arranged to act in response to drive signals generated by the sensor member (3) in its working position.